Any of you guys that have been to the track. When you launch in 4wd can you shift the truck back to 2wd. Will it actually shift out of 4wd or b/c its under power just stay in 4wd? Just curious.

 

It'll stay in 4wd. Theres so much torque on everything that it wont unlock till you let off the throttle. Besides, thats one more distraction while you're speeding down the strip. Just remember to take it out before you turn at the end.

 

I have tested the 2 by 4 by thing but on a manual select setup. If you have ESOF, don't bother as you run the risk of braking stuff shifting it and I don't think it will anyway. Besides, the 4by was faster. This on the 1/8 strip but I wonder if I might do a bit better in the 2by on the 1/4. There are now some serious traction issues in 2wd so I don't know. Others will chime in.

 

4wd all the way down the track. That's what everyone else does, including the big boys.

 

In 2wd, when I hit 15# boost, my rear tires start breaking loose. I can boost to 10# then hammer it and my tires will start spinning. I have to feather the throttle in order not to spin the tires in 2wd.

In 4wd, I can boost to 20# then let off the brake and it will launch like a scalded dog. I have had people tell me a dually is not supposed to be able to do this. Well, I tell them a stock one can't.

 

IMHO,the time that you make up in the 60 ft by being having the added traction that being in 4wd allows, more than offsets the loss of time at the top due to any added friction from the drive train.

 

Thanks for the info guys. At what boost do you guys launch your truck in 4WD. I have only ran my truck 3 times and the last time i ran it, i launched it at about 8 lbs. of boost. What is the normal? What is kinda the safe side without worrying about breaking anything?

 

The big thing you have to worry about is building boost and waiting for too long. The PCM will read the boost and see that the tires aren't moving and go into a limp mode. It happened to Kris when we were at smokin'. Don't sit there for more than 5-7 seconds. As far as what boost number to leave at, it all depends on the traction you are getting. It will vary by track conditions, and how sticky your tires are. You are gonna have to play with it.

 

I posted my boost #'s in my previous post. I have not broken anything yet, but in 4wd I boost to 20#. I don't know the norm for this, just what I do.

 

I've launched with 12 once (thats the highest it would go sitting there). That was basically me standing on the brake and about 2/3 throttle IIRC. As soon as I let off the brake, I went full throttle. Any kind of boost launch is hard on the tranny. If you're doing this often, make sure you have a good cooler (which you do) and keep an eye on the fluid to make sure you dont cook it. Oh, and dont be surprised if you break something some day

 

Slinging the front driveshaft and aerating the oil pan are my biggest fears.

 

Is that what he told you?

 

Just a small correction here...you need to worry about building RPM too long, not boost. The PCM will see the engine has RPM but not see any speed on the output shaft of the trans. After a short time, the PCM sees this difference as an error, that the speed sensor on the output shaft is not working. This can actually cause the truck to shift into 2nd gear even though it's not moving. This is from Brian (of BTS), after I asked him about it becaus it happened to me and I had no idea what it was. I've also seen a few torque converters take a dump during that time of extended RPM with no movement.

What I do that has worked well for me is to wait for both sets of the staging lights to become lit on both sides. As soon as the last bottom set gets lit, whether it's you or the other person, then put the throttle down while holding the brake. As soon as the third yellow light comes on, release the brake and floor the throttle. This will minimize the time that you're having RPM's up with no movement. Using this exact technique, I was cutting low 0.5's on a 0.500 tree last summer.

The above is assuming you're running heads up, and not a bracket race where you might have a delay. If you're bracket racing and you're the quicker truck, you'll have to plan for the delay. In bracket racing, consistency is the key, so if you're in a bracket race, just try to be consistent...like not hitting the throttle until the first yellow lights. Sure, your boost may not be up as much as possible for the hardest launch, but it will be consistent, which is what you'd be after in that case.

 

Thanks for the info guys, i'll play with it some more next time i go to the track.